1. Technical Field
The present invention generally relates to a material handling apparatus and, in a preferred embodiment thereof, more particularly relates to an excavating apparatus, representatively a tracked excavator, having operatively attached to the stick portion of its boom a specially designed combination bucket and breaker structure which uniquely permits the excavator operator to selectively carry out either digging or refusal material breaking tasks without having to change out equipment on the stick.
2. Description of Related Art
Large scale earth excavation operations are typically performed using a powered excavating apparatus, such as a tracked excavator, having an articulated, hydraulically pivotable boom structure with an elongated, pivotal outer end portion commonly referred to as a xe2x80x9cstick xe2x80x9d. Secured to the outer end of the stick is an excavating bucket which is hydraulically pivotable relative to the stick between xe2x80x9cclosedxe2x80x9d and xe2x80x9copenxe2x80x9d positions. By pivotally manipulating the stick, with the bucket swung to a selected operating position, the excavator operator uses the bucket to forcibly dig into the ground, scoop up a quantity of dirt, and move the scooped up dirt quantity to another location, such as into the bed of an appropriately positioned dump truck.
A common occurrence during this conventional digging operation is that the bucket strikes refusal material (in excavation parlance, a material which xe2x80x9crefusesxe2x80x9d to be dug up) such as rock which simply cannot be broken and scooped up by the bucket. When this occurs it is typical practice to stop the digging operation, remove the bucket from the stick, and install a hydraulically operated xe2x80x9cbreakerxe2x80x9d on the outer end of the stick in place of the removed bucket. The breaker has, on its outer end, an oscillating tool portion which rapidly hammers the refusal material in a manner breaking it up into portions which can be subsequently dug up. After the breaker has been utilized to break up the refusal material, the operator removes the breaker from the stick, replaces the breaker with the previously removed bucket, and resumes the digging operation with the bucket.
While this procedure is easy to describe, it is a difficult, laborious and time-consuming task for the operator to actually carry out due to the great size and weight of both the bucket and breaker which must be attached to and then removed from the stick, and the necessity for the operator to climb into and out of the high cab area of the excavator (often in inclement weather) to effect each bucket and breaker changeout on the stick. This sequence of bucket/breaker/bucket changeout, of course, must be laboriously repeated each time a significant refusal area is encountered in the overall digging process.
A previously utilized alternative to this single excavator sequence is to simply provide two excavators for each digging projectxe2x80x94one excavator having a bucket attached to its boom stick, and the second excavator having a breaker attached to its boom stick. When the bucket-equipped excavator encounters refusal material during the digging process, it is simply moved away from the digging site, and the operator climbs down from the bucket-equipped excavator, walks over to and climbs up into the breaker-equipped excavator, drives the breaker-equipped excavator to the digging site, and breaks up the encountered refusal material. Reversing the process, the operator then switches to the bucket-equipped excavator and resumes the digging process to scoop up the now broken-up refusal material.
While this digging/breaking technique is easier on the operator, it is necessary to dedicate two large and costly excavators to a given digging task, thereby substantially increasing the total cost of a given excavation task. A modification of this technique is to use two operatorsxe2x80x94one to operate the bucket-equipped excavator, and one to operate the breaker-equipped excavator. This, of course, undesirably increases both the manpower and equipment cost for a given excavation project.
Another attempt to solve this problem is disclosed in U.S. Pat. Nos. 6,085,446 and 4,100,688 for an excavating machine having a motorized milling tool attached to the back of the bucket. A primary disadvantage of these devices is complexity, cost, and reliability. Another disadvantage is the weight that must be continuously carried by the bucket. The additional weight substantially reduces the carrying capacity and mobility of the bucket. Another disadvantage to the device of U.S. Pat. No. 6,085,446 is that the back of the bucket cannot be used to smooth or pad the soil, as is a well-known practice in the industry. Another disadvantage is that surface rock is not subject to an overburden pressure, so it generally fails faster under compression and impact forces than by the shearing forces of a scrapping and gouging rotary drilling tool.
Another attempt to solve this problem is disclosed in U.S. Pat. No. 4,070,772 for an excavating machine having a hydraulic breaker housed inside, or on top of, the boom stick. A primary disadvantage of this device is that it is extremely complex and expensive. Another disadvantage of this device is that it cannot be retrofit to existing excavators. Another disadvantage of this device is that the size of the breaker is limited. Another disadvantage of this device is that the bucket must be fully stowed to access the breaker and vice versa, making simultaneous operation impractical.
A more recent attempt to solve this problem is disclosed in U.S. Pat. No. 5,689,905 for another excavating machine having a hydraulic breaker housed inside, or on top of, the boom stick. In this device, the chisel portion of the breaker is removed when not in use. A primary disadvantage of this device is that it fails to permit immediate, unassisted switching from breaker to bucket, and thus simultaneous operation is impossible. Another disadvantage of this device is that it requires manual handling of the extremely heavy chisel tool each time the operator desires to convert to a breaker or bucket operation. Another disadvantage of this device is that it is extremely complex and expensive. Another disadvantage of this device is that it cannot be retrofit to existing excavators.
As can be readily appreciated from the foregoing, a need exists for an improved technique for carrying out the requisite digging and refusal material-breaking portions of an overall excavation operation in a manner eliminating or at least substantially eliminating the above-mentioned problems, limitations and disadvantages commonly associated with conventional digging and breaking operations. It is to this need that the present invention is directed.
In carrying out principles of the present invention, in accordance with a preferred embodiment thereof, an excavating machine, representatively a tracked excavator, is provided with a specially designed pivotable boom stick assembly that includes a boom stick having first and second excavating tools secured thereto for movement relative to the boom stick. Illustratively, the first excavating tool is an excavating bucket secured to the boom stick for pivotal movement relative thereto between a first position and a second position, and the second tool is a breaker secured to the boom stick for pivotal movement relative thereto between a stowed position and an operative position.
A hydraulically operable drive apparatus is interconnected between the boom stick and the bucket and breaker and is useable to pivotally move the bucket between its first and second positions, and to pivotally move the breaker between its stowed and operative positions. Representatively, the drive apparatus includes a plurality of hydraulic cylinder assemblies operatively interconnected between the boom stick and the bucket and breaker.
The bucket, when the breaker is in its stowed position, is movable by the drive apparatus to the second bucket position and is useable in conjunction with the boom stick, and independently of the breaker, to perform a digging operation. The breaker, when the bucket is in its first position, is movable by the drive apparatus to the breaker""s operative position and is useable in conjunction with the boom stick, and independently of the bucket, to perform a breaking operation. Accordingly, the excavating machine may be advantageously utilized to perform both digging and breaking operations without equipment changeout on the boom stick.
Another advantage of the present invention is that the bucket can be operated without fully stowing the breaker. Likewise, the breaker may be operated without the necessity to fully extend the bucket. This increases the efficiency of the excavation process by providing immediate access to each of the tools, without delay. Another advantage of this capability is that it further increases the efficiency of the excavation process by rendering the bucket available to frequently scrape away the freshly generated cuttings so the breaker tool is always exposed to fresh refusal material, avoiding operation against previously generated cuttings. Another advantage of this capability is that by avoiding operation against previously generated cuttings, the breaker tool will last longer.
In an illustrated preferred embodiment thereof, the excavating machine is also provided with control circuitry coupled to the drive apparatus and useable to operate it. Representatively, the control circuitry includes a hydraulic flow circuit in which the drive apparatus is interposed; a flow controller operative to electively reverse the direction of hydraulic fluid flow through a portion of the hydraulic flow circuit; a diverting valve apparatus interconnected in the hydraulic flow circuit and operable to selectively route hydraulic fluid through the hydraulic flow circuit to (1) a first portion of the drive apparatus associated with the bucket, or (2) a second portion of the drive apparatus associated with the breaker; and a switch structure useable to selectively operate the diverting valve apparatus.
In another illustrated preferred embodiment of the present invention, a breaker and deployment system is disclosed, having a mounting bracket attached to the underside and lower end of the boom stick. A breaker is pivotally attached to a first pivot on the bracket. In the preferred embodiment, the first pivot is bifurcated. A hydraulic cylinder is pivotally attached at a second pivot on the bracket, in close proximity to the first pivot. The hydraulic cylinder is pivotally attached to the breaker at a third pivot. This embodiment has the advantage of requiring only one hydraulic cylinder. This embodiment has the additional advantage of using a much shorter hydraulic cylinder. This embodiment has the additional advantage of rapid deployment and retraction of the breaker. This embodiment has the additional advantage of a more stable and durable assembly during use. This embodiment has the additional advantage of being much easier and faster to install or remove. This embodiment has the additional advantages of being less expensive to manufacture, install, and service. This embodiment has the additional advantage of resulting in an increased range of motion of the deployed tool. This embodiment has the additional advantage of providing protection for the hydraulic cylinder when the tool is deployed and operational. This embodiment has the additional advantage of resulting in a less obstructive configuration of the hydraulic cylinder in relation to the boom stick when deployed.
In another illustrated preferred embodiment of the present invention, a bracket is attached to the inside and lower end of the boom stick. A breaker is pivotally attached to a first pivot on the bracket. A latch-lock assembly is mounted to, and between, the boom stick and the breaker. This embodiment has the advantage of preventing undesired, partial deployment of the breaker from the vibration and impact forces encountered during operation of the bucket. In a preferred embodiment, the latch-lock assembly comprises a slide latch located in a guide box attached to the boom stick for latching engagement with a strike attached to the breaker assembly. In another preferred embodiment, the latch-lock assembly comprises a ball latch attached to the boom stick for latching engagement with a strike ball attached to the breaker assembly.
In another illustrated preferred embodiment of the present invention, a shock absorbing retraction stop is attached to the boom stick. This prevents damage to the breaker and the boom stick when the breaker is in the stowed position, encountering vibration and impact forces during operation of the bucket.
In another illustrated preferred embodiment of the present invention, a bracket is attached to the underside and lower end of the boom stick. A breaker is pivotally attached to a first pivot on the bracket. Deployment of the breaker is made by the force of gravity acting on the breaker, upon release of the latch-lock assembly. In this embodiment, a controllable hydraulic cylinder is unnecessary to forcibly move the breaker. The breaker may be stowed by retracting the bucket into the breaker, thus forcing it upwards and against the boom stick until the latch-lock assembly can be engaged to secure the breaker in place. This embodiment has the advantage of being easily retrofit onto excavating machines without modification of the hydraulic system. An additional advantage of this embodiment is the lower cost of materials and installation. Optional to this embodiment, an uncontrolled hydraulic or pneumatic cylinder may be used to prevent free fall of the breaker upon release of the latch-lock. An advantage of this embodiment is increased safety.
In another illustrated preferred embodiment of the present invention, a bracket is attached to the underside and lower end of the boom stick. An extension stop is attached to the bracket, engageable with the breaker. One advantage of this embodiment is that it adds to the operator""s control of the breaker tool. Another advantage of this embodiment is that the extension stop transmits a component of the impact force from the breaker directly to the boom stick, which reduces the reaction forces on the hydraulic cylinder, thus extending the life of the hydraulic cylinder. Another advantage of this embodiment is that the extension stop prevents over-extension of the breaker away from the boom stick, which has been shown to result in damage to the hydraulic cylinder used to deploy the breaker. Another advantage of this embodiment is that it is also useful in the gravity deployment embodiment disclosed above and elsewhere herein, to prevent excessive movement of the breaker during operation.